1. Field of the Invention
The present invention relates to an action part for a piano, which is pivotally moved along with depression of a key to thereby transmit key depression energy generated by depression of the key, to a hammer.
2. Description of the Related Art
In general, a wippen, which is one of action parts of a grand piano, is made of wood, and pivoted at a rear end thereof for pivotal motion thereabout (hereinafter, a forward side as viewed from the player is referred to as “the rear”). The wippen is placed on a rear part of a key. When pushed up by the key depressed, the wippen is pivotally moved upward, and causes other action parts, such as a jack, to be moved in an interlocked manner, thereby causing the hammer to pivotally move upward for striking a string stretched thereabove. After that, the wippen is pivotally moved downward by gravity, and brought into abutment with the rear part of the key, whereby the key is made ready for next depression. As described above, the wippen is one of essential action parts for transmitting key depression energy generated by depressing the key to the hammer. Further, an action is placed on the key via the wippen, as part of the action, so that the weight of the action is closely related to the touch weight of the key. The touch weight of the key is adjusted by a balance between a weight attached to a front portion of the key and the weight of the action.
An example of the wippen described above has been conventionally proposed e.g. in Japanese Laid-Open Utility Model Publication (Kokai) No. 62-146194. This wippen is made of a metal or a synthetic resin, or has a weight attached thereto, so as to increase the weight thereof. After once pivotally moved upward, the wippen increased in weight due to the above construction descends at an increased speed, whereby it is promptly brought into abutment with the key.
As described above, the wippen plays the role of a transmitter of key depression energy. In general, the wippen is made of wood, because wood is light in weight and high in rigidity, and hence is suitable for transmitting key depression energy. However, when compared with a synthetic resin, wood is inferior in machining accuracy, which makes troublesome the adjusting operations required in the manufacturing of actions. Further, wood has a larger dimensional change due to drying and wetting, which makes the wippen made of wood liable to be displaced in positional relationship with the other action parts. This makes it difficult to maintain normal motion of the action.
On the other hand, the wippen made of a synthetic resin does not suffer from the above inconveniences caused by the use of the wippen made of wood, but since the rigidity of synthetic resin is lower than that of wood, the pivotal motion of the hammer is reduced in speed. As a result, to obtain the same sound volume, a larger key depression energy is necessitated. Further, since synthetic resin has a larger specific gravity than that of wood, the motion of the wippen becomes slow, which lowers responsiveness of the action, resulting in the delayed timing for hammering the string. Further, the larger specific gravity of synthetic resin increase the weight of the whole action including the wippen, and hence to obtain the same touch weight as that of the wippen made of wood, it is necessary to increase the amount of the above-mentioned weight attached to the key.
The wippen made of metal does not suffer from the inconveniences causes by the use of the wippen made of wood, similarly to that made of synthetic resin, but since metal has a still larger specific gravity than that of synthetic resin, delay of the string-hammering timing and increase in the weight for the key become significant. This is also true in the case of the weight being attached to the wippen.